Live data from Hacker News

Open-source communications by bouncing signals off the Moon

open.space

31–40 of 88 posts

Re: Open-source communications by bouncing signals off the Moon

#31

For someone not well versed with the terminology, can someone please tell what kind of bitrate this can provide? In bytes per second.

A lightly coded (13/15 LDPC) 256QAM OFDM signal at 40 MHz wide could do 250 Mbps.

Or 31.25 million bytes per second if you prefer.

This would be for a point to point terrestrial link. OFDM probably wouldn't work for EME (at any power level).

Re: Open-source communications by bouncing signals off the Moon

#32
post #29

Earlier quoted context omitted.

It's not even a byte per second. The latency of the distances involved mean you're looking at around two seconds per round trip, plus a little extra because of the fuzziness of radio in space and absolutely everything that can distort it. There's a lot of math that goes into selecting the right bit-width for the signal, which I ain't doing here and now [0], but most 24dB things tend to be 32bit for reasons. The array…

Thank you so much. Are these rough calculations based on the smallest (quad), mini or the large array?

That was for the large array, assuming you were bouncing from you to moon and back again.

Point-to-point on the Earth would actually be semi-decent, as another comment pointed out.

Re: Open-source communications by bouncing signals off the Moon

#33
post #29

For someone not well versed with the terminology, can someone please tell what kind of bitrate this can provide? In bytes per second.

It's not even a byte per second. The latency of the distances involved mean you're looking at around two seconds per round trip, plus a little extra because of the fuzziness of radio in space and absolutely everything that can distort it. There's a lot of math that goes into selecting the right bit-width for the signal, which I ain't doing here and now [0], but most 24dB things tend to be 32bit for reasons. The array…

No, if you do the math it's about 40 bytes per second (300bps) for Earth-Moon-Earth using their 240-antenna array.

Re: Open-source communications by bouncing signals off the Moon

#35
post #29

Earlier quoted context omitted.

It's not even a byte per second. The latency of the distances involved mean you're looking at around two seconds per round trip, plus a little extra because of the fuzziness of radio in space and absolutely everything that can distort it. There's a lot of math that goes into selecting the right bit-width for the signal, which I ain't doing here and now [0], but most 24dB things tend to be 32bit for reasons. The array…

No, if you do the math it's about 40 bytes per second (300bps) for Earth-Moon-Earth using their 240-antenna array.

Care to share the math, if you've done it?

It's 1.3 to 1.6 seconds each way to the moon, by radio link.

JPL's much, much, much bigger arrays can only achieve 64kbps.

Re: Open-source communications by bouncing signals off the Moon

#36
post #35

Earlier quoted context omitted.

No, if you do the math it's about 40 bytes per second (300bps) for Earth-Moon-Earth using their 240-antenna array.

Care to share the math, if you've done it? It's 1.3 to 1.6 seconds each way to the moon, by radio link. JPL's much, much, much bigger arrays can only achieve 64kbps.

I dont get it, How does latency affect bandwidth here?

Re: Open-source communications by bouncing signals off the Moon

#37

KA1GT recently found a $100 “solar cooker” dish on AliExpress. Also available on Amazon. It was tested back in August. Announced on the EME Facebook Group: https://www.facebook.com/share/p/19zLsGZiE7/?mibextid=wwXIfr Output power was 500w

There's nothing that can't be modulated. Lol.

Re: Open-source communications by bouncing signals off the Moon

#38
post #35

Earlier quoted context omitted.

No, if you do the math it's about 40 bytes per second (300bps) for Earth-Moon-Earth using their 240-antenna array.

Care to share the math, if you've done it? It's 1.3 to 1.6 seconds each way to the moon, by radio link. JPL's much, much, much bigger arrays can only achieve 64kbps.

[deleted]

Re: Open-source communications by bouncing signals off the Moon

#39
post #38
post #35

Earlier quoted context omitted.

Care to share the math, if you've done it? It's 1.3 to 1.6 seconds each way to the moon, by radio link. JPL's much, much, much bigger arrays can only achieve 64kbps.

[deleted]

That would be with laser, which isn't really relevant here?

Re: Open-source communications by bouncing signals off the Moon

#40
post #36
post #35

Earlier quoted context omitted.

Care to share the math, if you've done it? It's 1.3 to 1.6 seconds each way to the moon, by radio link. JPL's much, much, much bigger arrays can only achieve 64kbps.

I dont get it, How does latency affect bandwidth here?

Because we're not stationary, and nor is the moon. Latency means greater dispersion, and lower successful return rates.
Post reply on HN